Omnidirectional impact switch



G. T. BOSWELL OMNIDIRECTIONAL IMPACT SWITCH July 22, 1969 5 Sheets-Sheet 1 Filed June 20,- 1967 I N VE NTOR 60R6 T BOSWELL A'I'TORNIiTY July 22, 1969 G. T. BOSWELL OMNIDIRECTIONAL IMPACT SWITCH 5 Sheets-Sheet 2 Filed June 20, 1967 INVENTOR Geokes TBasnqsLL ATTORNEY July 22, 1969 e. T. BOSWELL QMNIDIRECTIONAL IMPACT SWITCH 5 Sheets-Sheet 5 led-June 20, 1967 INVIJNIUR 650K615 ffiosmaz ATTOR N FY United States Patent O 3,457,382 OMNIDIRECTIONAL IMPACT SWITCH George T. Boswell, Springfield, Va., assignor to The Susquehanna Corporation, Fairfax County, Va., a

corporation of Virginia Filed June 20, 1967, Ser. No. 647,355 Int. Cl. Hillh 35/02, 35/14 US. Cl. 20061.45 9 Claims ABSTRACT OF THE DISCLOSURE An impact weight is releasably engaged, supported, and caged by a plurality of spring-like supports which also releasably engage a spring-loaded operator and hold it in the cocked position. The weight moves in response to impact or a predetermined level of vibration to dislodge the supports and allow the operator to be driven home by the spring.

BACKGROUND OF THE INVENTION Field This invention relates generally to fuzes with impact switches. The impact switch can be used in any environment other than that of fuzes, in which it is deisred to sense and respond to impact or vibration.

Prior art The two most important requirements in the design of a fuze for any ordnance item are safety and reliability. In the case of the former, the prior art shows many approaches, with the most accepted being that of mechanically locking the firing pin until the expiration of a certain amount of time or the happening of a certain event, so that it is highly unlikely that the fuze can fire while the ordnance item is still in close proximity to the user. The second problem, that of reliability, has been much more ditficult to solve, especially in the case of a double-acting, time-impact fuze. As evidenced by the prior art, the result of designing a double-acting fuze has been a complicated mechanism which is expensive to manufacture and is subject to a high rate of failure in the field. These fuzes usually embody a sensitive percussion device consisting of a detonator and a striking member in telescopic relation to each other, together with some sort of intercepting mechanical safety device to prevent premature contact of these parts. At first blush this system does not lend itself well to responding to impact in any direction. In order to achieve omnidirectional impact explosion characteristics, this telescopic firing pin mechanism must be mounted so that it will always point in the direction of impact or in such a manner as to be driven home no matter what the direction of impact. The most exemplary showing of this concept is that of Patent No. 2,763,212, Selective Time Impact Fuze for Hand Grenades, issued Sept. 18, 1956 to I. F. McCaslin. Another interesting concept is set forth in Patent No. 2,714,- 353 issued Aug. 2, 1955 to H. W. Greer. A third concept now being utilized in the art is that of a completely electrically operated fuze, having a battery activated by some happening after launch to arm an electric igniter which will fire on impact or upon cycling of some electrical means such as the full charging of a capacitor. All three of the concepts above recited, plus the many others advanced in the art, purport to advance as their main considerations safety and reliability. However, in all of them it has been diificult to reconcile the two. For example, Patent No. 2,763,212 and the electrical devices are extremely safe fuzes but are made so at the expense of a very complicated mechanism, while in the concept ad- 3,457,382 Patented July 22, 1969 vanced by Patent No. 2,714,353, the mechanism is made simple at the expense of safety.

SUMMARY OF THE INVENTION This invention provides a novel impact switch and a fuze which is both safe and reliable and which contains a minimum number of parts. The switch consists of a plurality of supports engaging a spring-loaded operator. In addition to engaging the operator and holding it in its biased condition away from the detonator, these support members also cage and support within their envelope a movable impact weight, which will by its inertial movement upon impact of the fuze dislodge at least one of the support members from its proper position, so unbalancing the equilibrium of the mechanism as to allow the other support members to be dislodged by the force of the spring behind the operator.

THE DRAWINGS FIGURE 1 is a perspective view of the impact weight and supports;

FIGURE 2 is a side elevation, in cross section, of an alternative arrangement of the impact weight of FIG- URE 1;

FIGURE 3 is a side elevation, in cross section, of a complete impact switch before operating;

FIGURE 4 is a side elevation, in cross section, of the switch of FIGURE 3 after operating;

FIGURE 5 is a side elevation, in cross section, of an alternative embodiment of the impact switch of FIG- URE 3;

FIGURE 6 is a side elevation, in cross section, of an alternative embodiment of the impact switch;

FIGURE 7 is a side elevation, in cross section, of a fuze utilizing the impact switch of FIGURE 3;

FIGURE 8 is the fuze of FIGURE 7 after firing by impact;

FIGURE 9 is the fuze of FIGURE 7 after firing by time delay;

FIGURE 10 is an alternative embodiment of the fuze utilizing the impact switch of FIGURE 6; and

FIGURE 11 is the fuze of FIGURE 10 after firing by impact.

DESCRIPTION OF THE IMPACT SWITCH A basic component of the fuze hereinafter described is an impact-sensing switch of novel design. This impact switch responds to impact in any direction to release a spring-loaded operator to actuate a detonator, close elec trical contacts, or perform like operation-s. As shown in FIGURE 1, the impact switch consists, in its most basic form, of an impact-responsive weight 10 which is engaged, supported, and caged by a plurality of supports 12 which can be of configuration somewhat like leaf springs. These supports 12 are shaped in the center section to engage weight 10 and are adapted to be mounted at 14 on the casing of the switch and to engage the operator at 16. An alternative configuration is illustrated in FIG- URE 2, where-in weight 10 is engaged by inserts 18 which together with spring members 20 and 22 form the supports for the weight and the operator. As in FIGURE 1, each of the supports has a mounting portion 14 and a portion 16 which engages the operator.

FIGURE 3 shows all the parts necessary for an operating switch. Impact weight 10 is provided with a passage 24 through the center and through this passage an operator 26 protrudes. Operator 26 has a stem portion 28 which extends through passage 24 and is adapted to contact means such as an electrical switch 30 upon release, and a head portion 32 which is releasably engaged by portions 16 of support elements 12. Operator 26 is biased toward the switch 30 by means such as a compression spring 34, but is prevented from moving under the influence of this bias so long as supports 12 engage the head portion 32 of operator 26. FIGURE 4 shows position of the various elements after the switch has operated. Weight 10 responds to impact of the switch, or a predetermined amount of vibration, to dislodge one or more of supports 12 from beneath the head 32 of operator 26, thus allowing the supporting system to collapse and operator to be driven into the switch by the force of spring 34.

The concept expressed in FIGURES 1 through 4 can also be manifested into another arrangement of components, as is shown in FIGURE 5. In this showing, the arrangement of weight 10 and supports 12 is identical to that described above except that the portion 16 of supports 12 are so designed as to engage and hold an operator 26 which is oriented in the opposite direction to that shown in the FIGURES 3 and 4. In FIGURE 5 operator 26 further includes an annular collar 36 which is engaged by a tension spring 34 which is trying to pull it away from the engagement of elements 12. The operation is almost identical to that of the switch previously described, except that upon sensing of impact or vibration by weight portions 16 of the supports disengage from around surface of head 32 thus allowing the tension spring to pull operator 26 away to strike the switch means 30.

Another variation on the basic design is shown in FIG- URE 6 wherein, in addition to the components described in the other figures, a loosely mounted annular ring or washer 38 is provided around the stem of operator 26. Portions 1-6 of supports 12 engage this washer 38 which, in turn, is in engagement with the lower surface of head portion 32 of operator 26. Again, a compression spring 34 provides the motive force to drive operator 26 into switch contacts 30. In this embodiment, reaction of weight 10 causes supports 12 to be dislodged from under the tiltable washer which then causes the other remaining supports to collapse, freeing operator 26 so that it may be driven by spring 34. The advantage offered by this embodiment is that the supports do not engage inclined surfaces and thus the balance of the support system, i.e., the force needed to dislodge the supports, can be more precisely predicted and established.

The switch described above prov-ides a simple means for sensing impact in any direction or for sensing the achievement of a predetermined amplitude of vibration. Therefore, the switch becomes particularly useful when combined with an ordnance item which is intended to explode upon impact. As the description progresses, it is seen that this switch lends itself very well to combinations with various types of arming mechanisms, both explosive and mechanical, as well as many types of mechanical methods. Although described throughout the remainder of this specification as installed in a grenade fuze, obviously the switch has many more applications and the invention should not be considered as being restricted to this particular environment.

DESCRIPTION OF THE FUZE The basic design of the fuze is shown in FIGURE 7. Although the fuze casing is of cylindrical configuration and the elements of the assembly are arranged along the axis of said cylinder, this is not to be construed to mean that the construction is limited to the configuration shown here. The concept may, with equal ease, be applied to other designs and arrangements of components parts.

For purposes of best illustration, the fuze consists of a cylindrical casing 111 having a longitudinal axis 112 hereinafter called the support axis. A primer 114 is positioned at one end of the cylinder, and a detonator 116 is positioned at the other end thereof. Primer 114 is fired by any conventional means such as a pin or a trigger of conventional design, which is not shown and does not form a part of the instant invention. The firing of primer 114 begins the chain of events which results in the firing of detonator 116, in communication with the main explosive charge of the ordnance item, not shown. Detonator 116 is exploded by the action of the impact-sensing switch described in FIGURES 1-6, the action of which is manifested in operator 118, which comprises a firing pin 119, a head and an annular upward projecting flange 121. Flange 121 contains a series of flame passages 122, the purpose for which will be explained below. Operator 118 is positioned along the axis 112 in juxtaposition to detonator 116 and is biased toward detonator 116 by means such as a compression spring 124. Acting against the spring to hold operator 118 away from detonator 116 are a plurality of supports 126, which may be in the form of leaf springs and which are spaced from the detonator 116 and mounted on an annular spacer 128. Supports 126 do not act directly on head portion 120 of operator 118, nor are they attached thereto, but engage the lower lip of an impact piston 131 which is concentrically positioned about operator 118. Impact piston 131 does not engage the head portion 120 but acts on flange 122 through interposed cylindrical combustible spacer 132. The purpose and operation of this combustible spacer will be explained below. Held by supports 126 and, in fact, caged thereby, is an impact weight 134. Weight 134 has a hollow center through which the firing pin 119 of operator 118 passes. The design of the outer surface of impact weight 134 is such that it is complementary to the design of the support 126. Weight 134 is free to move in any direction.

Concentrically positioned about impact piston 131 and restraining compression spring 124, is a safety cage 136. This element comprises a shoulder 138 upon which compression spring 124 acts, and a skirt portion which is designed to engage and cage the removable supports 126 and weight 134 against outward movement. Safety cage 136 is movable between a first position in which skirt 140 engages and locks the firing pin and a second position, toward which it is biased by spring 124, in which the support elements are free to move radially outwardly. This position is illustrated in FIGURE 8. Movement to this second position is initially precluded by a combustible spacer 142, the operation of which will hereinafter be explained.

The final element essential to the fuze is a pyrotechnic delay element 144 which is positioned along axis 112 inside the concentrically positioned safety cage, impact piston and compression spring. This element is a delay train, the upper portion of which is ignited by primer 114. Pyrotechnic element 144 is also in communication with combustible spacer 142 and, after a predetermined length of burning, ignites it. In addition, pyrotechnic element 144 ignites combustible spacer 132 upon the end of the burning of the delay train, through flame passage ports 122 in the flange portion 121 of operator 118.

OPERATION OF THE FUZE This fuze is designed to operate in two modes, in response to impact and in response to the expiration of a predetermined time. In addition, the fuze incorporates a safety feature so that the impact mode of operation is impossible until a predetermined time after activation of the fuze. Contrary to those fuzes generally used in the prior art, the present fuze incorporates a single delay train which performs the double function of uncaging the impact firing mechanism and firing the fuze should there be no impact within a predetermined length of time. It also utilizes a novel impact sensing switch which is truly omnidirectional in response.

The fuze as assembled and ready for use has the parts in the interrelationship shown in FIGURE 7. That is, spring 124 is compressed and is attempting to act both on operator 118, which is restrained from movement by removable supports 126 and safety slide 134, which is restrained from movement by combustible spacer 142. The fuze is then inserted in the ordnance item, for example, a hand grenade. When the grenade is to be thrown, the primer 114 is fired by conventional means such as pulling the pin or pressing a trigger. Upon the firing of primer 114, pyrotechnic delay train 144 is ignlted and begins to burn at a predetermined rate. By thls time, the hand grenade has been thrown. Pyrotechnic element 144 burns for a predetermined length and then it passes and ignites combustible spacer 142, which is made of material which is fast burning and thus quickly consumed. The pyrotechnic delay train 144 continues to burn. Once combustible spacer 142 has been removed, safety cage 136 is free to move upwards, as pictured in FIGURES, in response to the biasing action of compression spring 124. When the safety cage 136 is moved upward, the skirt section 140 disengages from the support members 126 thus leaving them free to be moved outward radially. The impact mechanism is now armed. Upon impact of the grenade in any direction, impact weight 118 will be caused to move and in so doing, will dislodge one or more of supports 126. The movement of one of the supports 126 out of the way upsets the equilibrium of the support system such that the force of compression spring 124 acting on flange 121 of operator 118 can drive the firing pin 119 home. Note a preferred arrangement of support means 126 wherein the upper ends of the support means contact a slightly inclined portion 130 of the impact piston and thus the support means not removed by action of impact weight 134 are easily pushed away by the power of spring 124. The firing of the detonator by thls means is shown in FIGURE 8. By caging impact weight 134 within the envelope subscribed by the support means 126, the weight will react to impact in any direction, including that along the axis of the casing.

If the fuze has not sensed impact within a predetermined time, it is exploded by the time-fuze portion of the mechanism. Pyrotechnic delay element 144 continues to burn after it has ignited combustible spacer 142, at which time safety slide 136 moves upward to uncage the impact sensing mechanism. Should there be no impact, the pyrotechnic delay element 144 continues to burn until it communicates with combustible spacer 132 by means of ports 122. Combustible spacer 132 is ignited and consumed. The removal of combustible spacer 132 enables compression spring 124, acting on flange 121, to drive operator 118 the distance required to strike and ignite detonator 116, as shown in FIGURE 9. When the fuze is fired by this time mode, rather than impact, it is not necessary to remove or displace the supports 126, for they do not act directly on operator 118, but on impact piston 131, which also remains stationary.

A comparison between FIGURE 8 and FIGURE 9 shows that the main diiference between operation by the impact (FIGURE 8) and operation by time mode (FIG- URE 9), is that in the former, impact weight 134 removes supports 126 from beneath the impact piston 131, which is interlocked with operator 118, and the compression spring drives operator 118, combustible spacer 132, and the impact piston 131 towards the detonator. In the time mode, however, combustible spacer 132 has been consumed, but supports 126, holding the impact pistons 131, are still intact. The compression spring drives only operator 118 toward the detonator, with impact piston 131 and supports 126 remaining stationary. Either mode of fire is operated by a single pyrotechnic delay element and by the novel interrelationship between compression spring 124, operator 118, combustible spacer 132, and impact piston 131. The fuze operates mechanically in both modes using the same few pieces of hardware.

DESCRIPTION OF AN ALTERNATE FUZE The fuze described in the preceding paragraphs provides a basic time-impact fuze, but the concept is such that it lends itself well to modification by the addition of many accessory features in response to requirements for additional specific operating parameters and characteristics.

In addition to the safety features offered in the original fuze, FIGURE 10 shows a time-impact fuze into which is incorporated a mechanical safety means which precludes full movement of the firing pin until the fuze has been exposed to rotational forces. The impact-sensing switch used in the fuze of FIGURE 10 is the same as that shown diagrammatically in FIGURE 6. Construction of this fuze is similar to those described above, except that interposed between the firing pin 119 and the detonator 116, there are a plurality of small balls 152, of diameter greater than firing pin 119. These balls block passage 154 through which firing pin 119 must pass in order to strike the detonator. Attached to skirt portion of safety cage 136 is an element containing a trough 156, this trough being of such size and design as to provide a haven for the balls 152. Above the trough is a flange 158 which holds the balls in passage 154 in the initial stages of operation of the fuze. Skirt 140 also contains a plurality of indentations 155, into which certain of supports 126 can move when uncaged and knocked askew by the sensing of impact by weight 134.

In operation, the fuze works as follows: Prior to use the fuze components are arranged as shown in FIGURE 10, with balls 152 blocking passage 154 and being held in such position by the flange 158. Upon the firing of the initiator 114, powder train 144 is ignited and begins to burn, subsequently igniting consummable spacer 142, which burns away and allows the safety cage 136 to move upward. When the safety cage moves upward, trough 1 56 and flange 158 are also moved upward such distance as to align the opening of the trough with the balls 152. Impact weight 134 has now been uncaged and is free to operate in the normal manner, but balls 152 are still in position to block the movement of firing pin 119 and preclude initiation of detonator 116. However, when the weapon in which this fuze is installed is thrown, either by hand or from a barrel or launcher, and spin is imparted to it, balls 152 react to the centrifugal force to move outward into trough 156 thus clearing the way for the passage of firing pin 119. Once the spin arming sequence is completed, the fuze functions in the same manner as described above. Note, however, the difference in arrangement of components brought about by the use of the impact switch set out in FIGURE 6, rather than the type described in FIGURE 3. Upon impact, supports 126 are dislodged from beneath the washer 160 and the firing pin is driven home by the action of spring 124 against shoulder 121 of the operator 118. If no impact is sensed, powder train 144 burns to completion and through ports 122 communicates with and ignites combustible spacer 132, upon the collapse of which operator 118 can be moved by the spring in order to fire the detonator, notwithstanding the fact that supports 126 are still intact. The position of the components upon firing by impact are shown in FIGURE 11.

The fuzes described above have utilized explosive powder trains and consummable wafers in order to provide the sequence of safing and arming functions. However, it would be entirely feasible and possible to substitute for the explosive powder train 144, such mechanisms as spring motors, dashpots, or other timing devices, mechanical or electrical, to accomplish the same thing as explosive powder train. One could also substitute for igniter 114, electric means which would ignite the powder train or being the operation of the mechanical device substituted therefor.

It is thus seen that the instant invention provides a new and novel impact or vibration-sensing switch mechanism and a fuze incorporating said switch mechanism therein. The switch responds to impact or vibration in any direction, is simple in construction, and is easily provided with safing means. It is also easily adaptable for use with a multitude of accessories. Obviously, many modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

I claim: 1. An omnidirectional impact or vibration responsive switch, comprising:

an operator movable between a firs-t position and a second position, the movement of said operator being the output of said switch, biasing means urging said operator toward said second position, releasable means engaging said operator and holding said operator in said first position against the action of said biasing means, said releasable means comprising a plurality of resilient supports radially disposed about a support axis, one end of each of said supports being fixed and the other end thereof being movable and in releasable engagement with said operator, and a weight positioned within the envelope established by said radially disposed supports, said weight being releasably engaged and supported by said supports, whereby movement of said Weight in any direction in response to a predetermined degree of imp-act on or vibration of said switch causes dislodgment and removal of the movable ends of said supports from said operator, thereby allowing said operator to be moved to said second position by said biasing means. 2. The switch of claim 1 wherein said operator comprises a flange which is engaged by said supports.

3. The switch of claim 1 wherein each of said supports comprises a leaf spring having a curved portion releasably engaging and supporting said Weight.

4. The switch of claim 1 wherein each of said supports comprises a leaf spring having an outwardly extending portion releasably engaging and supporting said weight.

5. The switch of claim 1 wherein each of said supports comprises a center section having an indentation therein and releasably engaging said weight, said center section being interposed between two leaf spring outer sections.

6. The switch of claim 1 wherein said weight has a center passage therethrough, and said operator is longitudinally aligned and coincident with said support axis and extends through said passage.

7. An omnidirectional impact or vibration responsive switch, comprising:

an operator movable between a first position and a second position, the movement of said operator being the output of said switch, said operator having a tapered portion and a tiltable washer loosely positioned thereon and abutting said tapered portion, biasing means urging said operator toward said second position, releasable means engaging said washer and holding said operator in said first position against the action of said biasing means, said releasable means comprising a plurality of removable supports radially disposed about a support axis, one end of each of said supports being in releasable engagement with said washer, and a weight positioned within the envelope established by said radially disposed supports, said weight being releasably engaged and supported by said supports, whereby movement of said weight in any direction in response to a predetermined degree of impact on or vibration of said switch causes dislodgment and removal of said supports from said washer and tilting of said washer, thereby allowing said operator to be moved to said second position by said biasing means. 8. The switch of claim 7 wherein each of said supports comprises a resilient member having one end thereof in engagement with said washer.

9. The switch of claim 7 wherein each of said supports comprises a leaf spring having a fixed end, and a movable end in engagement with said washer.

References Cited UNITED STATES PATENTS 2,949,783 8/ 1960 Butler ZOO-61.45 X

FOREIGN PATENTS 1,077,761 5/ 1953 France.

ROBERT K. SCHAEFER, Primary Examiner R. A. VANDERHYE, Assistant Examiner US. Cl. X.R. 

